Study of anatomical organization of vertebrate brains, with particular emphsis on ascending sensory paths to the telencephalon, and intrinsic organization of the forebrain. Current projects include study of the ascending trigeminal sensory system to the forebrain, cells of origin, synaptic structure of terminal fields in the forebrain, local circuitry within the telencephalon and the origin of descending projections upon the trigeminal complex of the brainstem. Techniques employed include horse-radish peroxidase, autoradiography, Golgi methods, histochemistry and electron microscopy. Developmental studies are intended to demonstrate the time and sequence of development of the trigeminal sensory system nuclei and the establishment of synaptic relationship between constituent nuclei in the pigeons and chick during embryogenesis. The laminar organization of the optic tectum is being studied using HRP, ARG, Golgi, electron microscopy and histochemistry. Our main efforts at the present time are directed towards an analysis of non-retinal afferents. BIBLIOGRAPHIC REFERENCES: Polz-Tejera, Schmidt and Karten, Autoradiographic localization of el-bungarotoxin-binding sites in the central nervous system, Nature, 1975, Vol. 258, pp. 249-351. Benowitz and Karten, The Tractus Infundibuli and Other Afferents to the parahippocampal region of the pigeon, Brain Research, 1975, Vol. 102, pp. 174-180.